Explants of human benign hypertrophied prostate were cultured for 8 days. The effect of 5α-dihydrotestosterone on the morphology, DNA and glucose utilization of 14 cases was investigated. In four cases proliferation was clearly more extensive in the dihydrotestosterone-treated explants than in the controls. In six explants, there were no morphological differences between those cultured with or without dihydrotestosterone and in half of these, proliferation was present. Four explants were either necrotic or did not contain epithelial cells. The mean DNA content of the treated explants was higher than that of the controls (P < 0·01). There was no significant difference in the rate of glucose utilization by the explants treated with dihydrotestosterone, and by the controls.